package LC;

/**
 * https://leetcode.com/problems/unique-paths-ii/description/
 * Follow up for "Unique Paths":
 * Now consider if some obstacles are added to the grids.
 * How many unique paths would there be?
 * An obstacle and empty space is marked as 1 and 0 respectively in the grid.
 * For example,
 * There is one obstacle in the middle of a 3x3 grid as illustrated below.
 * [
 * [0,0,0],
 * [0,1,0],
 * [0,0,0]
 * ]
 * The total number of unique paths is 2.
 * Note: m and n will be at most 100.
 */
public class LC_063_UniquePathsII_DP {
    public static void main(String[] args) {
        int[][] a = new int[][]{
                {0, 0, 0, 0},
                {0, 1, 0, 0},
                {0, 0, 1, 0},
                {0, 0, 0, 0}
        };
        int n = Solution.uniquePathsWithObstacles(a);
        System.out.println(n);
    }

    static class Solution {
        public static int uniquePathsWithObstacles(int[][] obstacleGrid) {
            if (obstacleGrid == null || obstacleGrid.length == 0)
                return 0;
            int m = obstacleGrid.length;
            int n = obstacleGrid[0].length;
            int[][] dp = new int[m][n];

            for (int i = 0; i < m; i++) {
                if (obstacleGrid[i][0] != 1)
                    dp[i][0] = 1;
                else
                    break;
            }
            for (int j = 0; j < n; j++) {
                if (obstacleGrid[0][j] != 1)
                    dp[0][j] = 1;
                else
                    break;
            }
            for (int i = 1; i < m; i++) {
                for (int j = 1; j < n; j++) {
                    if (obstacleGrid[i][j] != 1)
                        dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                    else
                        dp[i][j] = 0;
                }
            }
            return dp[m - 1][n - 1];
        }
    }
}
